It is known in the prior art relating to scanners to scan workpieces such as flitches in a sawmill to detect defects such as stain, shake, knots, etc using so-called vision scanners and to map the profile of a workpiece including any wane edges. The results of such scanning is used to assist in optimizing further processing of the workpiece to recover the highest value and/or volume of pieces cut from the workpiece.
Scanners for use in sawmills, planermills, logdecks, engineered wood product machine centres such as veneer scanning, panel scanning and the like, or in other wood applications, may scan either lineally, that is, sequentially along the length of the workpiece as the workpiece is translated longitudinally through the scanner, or transversely, that is, simultaneously along the length of the workpiece as the workpiece passes through the scanner with the workpiece aligned transversely or laterally across the direction of flow of workpieces through the scanner. In the case of transverse scanning, conventionally the workpieces are delivered on an infeed such as an infeed employing a spaced apart parallel array of lugged transfer chains, smooth chains, belted transfers, etc. so as to pass each workpiece separately through a generally rectangular frame mounted laterally over and around the end of the infeed transfer. The scanner cameras and corresponding sources of illumination, such as halogen lamps, are typically mounted in the frame, often so as to simultaneously view both the top and bottom surfaces of the workpiece as the workpiece passes between the upper and lower beams or arms of the frame. Each camera has a pixel array aligned in a known orientation relative to the workpiece, for example aligned along the length of the workpiece. Light from the corresponding light sources is reflected from the surface of the workpiece and focussed by the camera lens onto the pixel array.
If the scanner is a profiling scanner, upper and lower triangulation geometry is used to arrive at a differential thickness measurement of the workpiece from movement of the focussed light along the array of pixels in the upper and lower cameras, from which a profile of the workpiece is modelled by an associated processor as a wireframe profile image. The accuracy or resolution of the wireframe model is influenced by the scan density, that is, the number of cameras and associated light sources, each of which generate the profile of a cross-section of the workpiece; the more closely spaced cross-sections, the higher the scan density and the better the accuracy or resolution of the wireframe model of the workpiece. The wireframe model of the workpiece is used by an optimizer, that is, a processor running optimization software, to determine optimized downstream cutting solutions for optimized recovery from the workpiece.
If the scanner is a vision scanner, the cameras, rather than being used to generate workpiece profile measurements, provide color and/or contrast data from the workpiece exterior surfaces within the field of view of each camera as the workpiece translates through the scanner. The color and/or contrast data is processed to generate predictions of the type and location of visually detectable defects on the workpiece surfaces. Defects may include holes, splits, shake, pitch pockets, knots, bark or wane, stain, etc.
It is understood that the present description of the background of the invention is not intended to limit the scope or ambit afforded the claims directed to the present invention as the background description merely reflects applicant's understanding of the present state of the art of wood processing. For example, the present invention is not intended to be restricted to either only vision scanning or profiling scanning or a combination of vision and profile scanning, whether in separate or in a single device or scanning package, as the present invention is intended to also include other forms of scanning such as multi-spectral, x-ray, microwave, etc.